Magnetic material



Patented Feb. 11, 1931 ,UNITED "STATES PATENT orrlcs GUSTAF w. um, 01' LEONIA, NEW JERSEY, ASSIGNOB TO BELL TELEPHONE LABO- BATOBIEB, INCORPORATED, 01' NEW YORK, N. Y., A CORPORATION OF NEW YORK MAGNETIC MATERIAL Io Drawing.

' The present invention relates to magnetic materials and to their ap lication to electromagnetic systems. They ave a wide field of usefulness and are of special interest in all 5 those cases in which the impressed magnetizing forces are small, such as in electric signaling systems.

Among the more important characteristics of the materials of this invention are high permeability, especially at low mafgnetizing forces, high degree of constancy o permeability over a considerable range of magnetizing forces, and high resistivity with consequent low eddy current losses.

In Elmens applications, Serial Nos. 119,622 and 119,623, filed June 30, 1926, there are de scribed and claimed magnetic compositions of iron, nickel, and cobalt which have been discovered to have, among other unusual properties, a very high degree of constancy of permeability over a wide range of magnetizmg forces including the low range employed in loaded signaling conductors. The uti 'ty of such compositions may be increased, es ecially for loading speech frequency or ot e r high frequenc circuits, by increasing their resistivity, if 's be done without excess vely or at all impairing other desirable propertles.

Brief mention 1s made in those specifications of the addition of fourth substances such as chromium to increase the resistivity. In

granted June 4, 1929, also Serial No. 220,387

filed September 19, 1927, which has issued as Patent 1,715,541, granted June 4, 1929, Serial No. 256,657, filed February 24, 1928, Serial issued .as Patent 1,715,543, 929 and Serial No. 289,050, filed June 28,

No. 287,017, filed June 20, 1928,'which has granted 'June 4,

Application fled Kay a1,

1928 'which has issued as Patent 1,715,648, granted June 4, 1929.

An object .of the present invention, therefore, is to increase the resistivity of magnetic materials having other desirable characteristics.

A further object is to reduce eddy current losses in magnetic materials of high initial permeability.

It has been found that by the addition of chromium in proper proportions, with or without other elements, and with appropriate heat treatments, compositions may be produced which have part or all of the desirable properties of the compositions described and claimed in application Serial No. 119,623 to a greater or lesser extent,-in some instances to the same extent as, or to a greater extent than without the added chromium,and in addition, a greatly increased resistivity. The production of ma etic comositions having the magnetic an electrica characteristics above discussed and which are workable and otherwise suitable for use is of considerable technical importance. Chromium is cheaper than molybdenum, which has been specifically claimed as a fourth element for increasin the resistivity of such compositions in an- 0t er ap composltions which are otherwise similar, gives a better combination of characteristics for certain purposes than does molybdenum.

Manganese may be added in addition to chromium to increase the workability or for other purposes in accordance with known metallurgical practice. Within the scope of the invention are included not only compositions of iron, nickel, and cobalt with chromium alone but also those including, in addition to chromium, molybdenum, tungsten, manganese, vanadium, tantalum, zirconium, chromium, copper and/or silicon.

The properties of compositions in accordance with the present invention may be varied over a wide range by the application of different heat treatments. A discussion of these heat treatments with-the general rules for their application in order to develop particular characteritics, is given in Patent No.

plication, and furthermore, in some.

1,715,541, dated June 4, 1929, and, therefore, is not repeated here.

A particular composition in accordance with the invention comprises 45% nickel, 27 iron, 25% cobalt, and 2% chromium. WVhen given a heat treatment desi nated L, in Patent 1,715,541, adapted to evelop a fairly constant, but not the greatest constancy of permeability, the initial permeability of 509 remains practically constant up to a value of H=about 1.7. .The composition had a maximum permeability of 2350 at H=3.10; a

hysteresis loss of 1120 at an induction of B==5100; an induction B of 13400 at H=; a remanence of 3460; a coercive force of 1.08; a resistivity of 44.35; an H for 1% change in rmeability of 1.75; and a percentage change in permeability for B 100 of .075. A heat treatment designed to develop a higher initial permeability gave a value thereof of 849 and a heat treatment designed to give a still hi her value of initial permeability gave a v ue of 1077.

A composition composed of approximately 51% nickel, 21% iron, 24% cobalt, 3% chromium, and 4% manganese had an initial permeability of 451 and a resistivity of 43 microhm cms. when heat treated to develop a fairly constant value of initial permeability. Other heat treatments gave initial permeabilities of 941 and 849, respectively.

A vir 'n alloy composed approximately of 45% nic el, 27% iron, 25% cobalt, 3% chromium, and 0.33% manganese exhibited an initial permeability of about 500, a high degree of constancy of permeability up to H=1.10 and a maximum permeability of about 3110 after heat treatment desi ated I in Patent 1,715,541. The increase in permeability between H=1.4 and H=2.1 was striking.

Another composition tested and found to have desirable magnetic properties consisted approximately of 29% iron, 45% nickel, 25% cobalt, and 1% chromium. Still another consisted of 22% iron, 50% nickel, 25% cobalt, and 3% chromium. The initial permeability of the last mentioned composition was about 440 when heat treated to develop a fairly constant permeability up to H=1.

A com osition composed approximately of 35% nic el, 27.5% iron, 35% cobalt, and 2.5% chromium, when heat treated in a manner adapted to develop constancy of permeability to a high but not the highest degree, had an initial permeability of 250 which was strikingly constant up to a magnetizing force of H=1.4. The hysteresis loss for a loop of which the maximum induction was about 5000 gauss was 1126 ergs per cubic centimeter per cycle. The remanence was 4490 gauss and the coercive force 1.25 gauss after an applied magetizing force of H==76. The resistivity was 46 microhm cms.

Still another composition composed of nickel, 12.5% iron, 15% cobalt, and 2.5%

able magnetic properties.

nickel-cobalt magnetic comppsitions in an amount up to 10 or 12% ena les one to produce a composition with a greatly increased resistivity, in combination with other desir- A number of compositions show increased initial permeability with from 2 to 10% chromium as compared to similar com ositions in which the chromi um is replace by iron.

These compositions disclose the characteristic properties of hi hly constant permeability over a range of fiux densities from zero upward, small or ne ligible hysteresis loss over a range of flux ensities from zero upward, initial permeability sufiiciently high to make them desirable for use in the magnetic circuits of telephone, telegraph and cable conductors and apparatus, the peculiar was waisted hysteresis loop characteristic of t e compositions discused in Patent No. 1,715,- 647, granted June 4, 1929, high resistivity, and workability in accordance with known methods.

In general, the nickel content may range from 10% to the cobalt content from 5% to 80%, the iron content from 9% to 50%, and the content of the chromium with or without still other elements up to about 10 or 12%.

Among the uses for which these materials are adapted are coil or lumped loading and continuous loading of carrier frequency signaling conductors in submarine and land line telegraphy and telephony, loading coils for composite telephone and telegraph systems, repeating coils or transformers, especially battery supply coils, wave filter coils, certain classes of relays, high frequency electromagnetic devices and magnetic circuits of electrical measuringinstruments.

What is claimed is:

1. A magnetic material including nickel between 10%and 80%, cobalt between 5% and 80%, and iron between 9% and 50% of the entire nickel-iron-cobalt content, heat treated to have desirable magnetic properties with small magnetizing forces, and including from a substantial quantity up to 12% chromium.

2. A composition in accordance with the foregoing claim which, in addition to chromium, includes material selected to include at least one of the following elements to a material extent; molybdenum, tungsten, manganese, vanadium, titanium, tantalum, zirconium, copper and silicon.

3. A composition in accordance with claim 1 heat treated to have an initial permeability above 200.

4. A composition in accordance with claim 1 heat treated to have an initial permeability m varying less than 1% up to magnetizing forces of .20 gauss.

5. A magnetic composition comprising between 30 and 60% nickel, between and 40% iron, between 5 and 50% cobalt, and

between 1 and 10% chromium, not excluding small amounts of other elements, heat treated to have desirable magnetic properties at small magnetizing forces.

In witness whereof, I hereunto subscribe my name this 29th da of May, 1929.

GU TAF W. ELMEN. 

